In recent years, a flexible device in which a semiconductor element, a light-emitting element, and the like are provided over a flexible substrate has been developed. Typical examples of the flexible device include, as well as a lighting device and an image display device, a variety of semiconductor circuits including a semiconductor element such as a transistor.
As a manufacturing method of a semiconductor device including a flexible substrate, a technique has been developed in which after a semiconductor element such as a thin film transistor is formed over a support substrate such as a glass substrate or a quartz substrate, the semiconductor element is transferred to a flexible substrate. In this technique, a step of peeling a layer including the semiconductor element from the support substrate is needed.
For example, Patent Document 1 discloses the following peeling technique using laser ablation: a separation layer formed of amorphous silicon or the like is formed over a substrate, a layer to be peeled which is formed of a thin film element is formed over the separation layer, and the layer to be peeled is bonded to a transfer body with the use of a bonding layer. The separation layer is ablated by laser light irradiation, so that peeling is generated in the separation layer.
In addition, Patent Document 2 discloses the following peeling technique: a metal layer is formed between a substrate and an oxide layer and separation is generated at an interface between the oxide layer and the metal layer by utilizing weak bonding at the interface between the oxide layer and the metal layer, so that a layer to be peeled and the substrate are separated from each other.    [Patent Document 1] Japanese Published Patent Application No. H10-125931    [Patent Document 2] Japanese Published Patent Application No. 2003-174153